gluBuild2DMipmapLevels

gluBuild2DMipmapLevels: man2/gluBuild2DMipmapLevels.xml

gluBuild2DMipmapLevels builds a subset of prefiltered two-dimensional texture maps of decreasing resolutions called a mipmap. This is used for the antialiasing of texture mapped primitives. A return value of zero indicates success, otherwise a GLU error code is returned (see gluErrorString ). A series of mipmap levels from base to max is built by decimating data in half along both dimensions until size 1 × 1 is reached. At each level, each texel in the halved mipmap level is an average of the corresponding four texels in the larger mipmap level. (In the case of rectangular images, the decimation will ultimately reach an N × 1 or 1 × N configuration. Here, two texels are averaged instead.) glTexImage2D is called to load these mipmap levels from base to max. If max is larger than the highest mipmap level for the texture of the specified size, then a GLU error code is returned (see gluErrorString ) and nothing is loaded. For example, if level is 2 and width is 16 and height is 8, the following levels are possible: 16 × 8, 8 × 4, 4 × 2, 2 × 1, 1 × 1. These correspond to levels 2 through 6 respectively. If base is 3 and max is 5, then only mipmap levels 8 × 4, 4 × 2, and 2 × 1 are loaded. However, if max is 7, then an error is returned and nothing is loaded since max is larger than the highest mipmap level which is, in this case, 6. The highest mipmap level can be derived from the formula log 2 ⁡ max ⁡ width height × 2 level. See the glTexImage1D reference page for a description of the acceptable values for format parameter. See the glDrawPixels reference page for a description of the acceptable values for type parameter.

gluBuild2DMipmapLevels is only available if the GLU version is 1.3 or greater. Formats GLU_BGR, and GLU_BGRA, and types GLU_UNSIGNED_BYTE_3_3_2, GLU_UNSIGNED_BYTE_2_3_3_REV, GLU_UNSIGNED_SHORT_5_6_5, GLU_UNSIGNED_SHORT_5_6_5_REV, GLU_UNSIGNED_SHORT_4_4_4_4, GLU_UNSIGNED_SHORT_4_4_4_4_REV, GLU_UNSIGNED_SHORT_5_5_5_1, GLU_UNSIGNED_SHORT_1_5_5_5_REV, GLU_UNSIGNED_INT_8_8_8_8, GLU_UNSIGNED_INT_8_8_8_8_REV, GLU_UNSIGNED_INT_10_10_10_2, and GLU_UNSIGNED_INT_2_10_10_10_REV are only available if the GL version is 1.2 or greater.